DIGESTION. 



15 



other saccharine juices, procured from certain 

 tropical plants, are employed for the same pur- 

 pose. The fermented liquors of our own coun- 

 try generally contain a considerable quantity of 

 mucilaginous and saccharine matter, which still 

 remains undecomposed, and which is directly 

 nutritive; but fully fermented wines are only 

 indirectly so, as aiding the digestive powers 

 by their stimulating effect on the stomach. 



It is generally admitted, that the operation 

 of alcohol, when properly diluted, and when 

 taken in moderate quantity, is favourable to the 

 health of most individuals who are engaged in 

 laborious pursuits, and have occasion to exert 

 the full powers of the system. But the almost 

 irresistible temptation to excess, and the fatal 

 consequences which thence ensue, both to our 

 physical and our mental constitution, have long 

 been the subject of deep regret and severe re- 

 prehension, both to the physician and the mo- 

 ralist, and it may be asserted, that of all the 

 gifts which providence has bestowed on the 

 human race, there is none which, according to 

 the present state of society, would appear of 

 such dubious advantage as the knowledge of 

 the process by which one of the most nutritive 

 articles of diet is converted into one of the 

 deadliest poisons. 



We have now to notice a class of substances 

 very generally employed in diet, which are not 

 in themselves nutritive, but are added to our 

 food, for the purpose of rendering it more agree- 

 able to the palate. These are the various arti- 

 cles styled condiments ; they may be classed 

 under the two heads of salts and spices. There 

 is so very general a disposition among all classes 

 of people in all countries to relish sapid food, 

 that we are led to conceive that there must be 

 some final cause for it, independent of the mere 

 gratification of the senses, or that this gratifica- 

 tion is made subservient to some more import- 

 ant purpose. With respect to what is termed 

 common salt, the muriate of soda, we observe, 

 in many cases, the same relish for it among the 

 lower animals as in man. We have well au- 

 thenticated accounts given us, by various tra- 

 vellers and naturalists, of the extraordinary 

 efforts which are made by the beasts of prey 

 which inhabit the great African and American 

 continents, to obtain it.* We can scarcely 

 therefore doubt that it must be, in some way or 

 other, essential to the well-being of the animal ; 

 but whether it directly promotes the process of 

 chjmification, or whether it be taken into the 

 stomach, for the purpose of being transmitted 

 to the blood, and thus furnishing to the system 

 the portion of saline matter which is always 

 present in the animal fluids, must be considered 

 as entirely conjectural.f 



The other division of condiments, the spices, 

 are very numerous, and are derived from vari- 

 ous sources, but are chiefly of vegetable origin. 

 They are generally of a stimulating nature, and 



* Among these we may select the account given 

 us by Mr. Hodgson, in his interesting letters from 

 North America, vol. i. p. 240, 1, note. 



t Haller, El. Phys. xix. 3, 11 ; Fordyce on 

 Digestion, p. 55. 



such as may be supposed to act, in the first in- 

 stance, on the nervous system. Some of them 

 increase the action of the heart and arteries, 

 and some of them augment the secretions or 

 excretions, but they differ essentially from 

 alcohol, in not producing any thing resembling 

 intoxication and the subsequent exhaustion. 

 Thus they are much less injurious to the con- 

 stitution, even when taken to excess, and are 

 seldom liable to any stronger imputation than 

 that of being useless. They afford some of the 

 most remarkable examples of the effect of habit 

 on the system, in changing or modifying our 

 original perceptions, for it is very generally 

 found that those substances to which we be- 

 come, in process of time, the most attached, 

 are such as, in the first instance, were not only 

 perfectly indifferent, but even positively dis- 

 gusting. 



Before we quit this part of the subject it 

 remains for us to say a few words respecting 

 the class of substances which are properly 

 termed medicaments. The medicaments are 

 nearly related to the condiments in their action 

 on the system, but with this difference, that 

 they are not only disagreeable to the palate, but 

 are, for the most part, incapable of being re- 

 conciled to it by habit. But there is in fact 

 no exact line of demarcation between them ; 

 many of the articles which are usually consi- 

 dered as condiments, being not unfrequently 

 used in medicine, and some of what are gene- 

 rally regarded as the most active and nauseous 

 medicines, being employed by some individuals 

 as agreeable condiments. Both these classes 

 of substances appear to differ in one essential 

 particular from what are more properly re- 

 garded as articles of diet, that while it is essen- 

 tial to the operation of the latter, that they 

 should be decomposed, and probably resolved 

 into their constituent elements, the specific 

 effect of the former seems to depend upon their 

 acting on the stomach in their entire state. 

 Nearly connected to this class of substances, 

 and indeed differing from it only in degree, are 

 the articles that are usually termed poisons. 

 The term may, however, be regarded as entirely 

 a popular designation, for as there is no active 

 medicine which may not immediately destroy 

 life by an excessive or improper administra- 

 tion, so there are no substances, among those 

 which are usually considered as poisonous, which 

 may not, under certain circumstances, prove 

 valuable medical agents. 



III. An account of the changes which the 

 food experiences in the process oj' digestion. 

 We now proceed to the consideration of the 

 third subject which we proposed for our in- 

 quiry, the nature of the change which the food 

 undergoes during the process of digestion. In 

 prosecuting this inquiry we shall consider in 

 succession the various processes by which the 

 aliment, after being received into the mouth, is 

 brought into the state of chyle. These changes 

 may be reduced essentially to three ; the me- 

 chanical division of the food, as effected by the 

 operations of maceration, mastication, and tri- 

 turation; the conversion of the alimentary mass 

 into chyme, by the action of the gastric juice; 



